Bleeding gums are not normal
Many people assume a little blood when brushing is simply what happens. It is not. Healthy gums do not bleed, and bleeding is almost always the earliest visible sign of inflammation.
The usual cause: gingivitis
By far the most common cause is plaque accumulating at the gum line. The resulting inflammation, gingivitis, is entirely reversible with thorough brushing, daily interdental cleaning and a professional scale and polish. Left alone, it can progress to periodontitis, which destroys the bone supporting the teeth and is not reversible.
Other contributing factors
Hormonal changes during pregnancy make gums more reactive to plaque. Smoking masks bleeding while making the underlying disease worse. Blood-thinning medication, vitamin deficiencies and some general health conditions can also play a part.
What to do
Do not stop brushing the area — inflamed gums need cleaning most. Brush gently but thoroughly, clean between the teeth daily, and book a check-up. If bleeding persists beyond two weeks of good hygiene, it needs professional assessment.